Takeaki Iwamoto

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Organization: Tohoku University , Japan
Department: Department of Chemistry
Title: Professor(PhD)

TOPICS

Co-reporter: Dr. Shintaro Ishida;Yoshifumi Misawa;Shohei Sugawara; Dr. Takeaki Iwamoto
Angewandte Chemie 2017 Volume 129(Issue 44) pp:14017-14020
Publication Date(Web):2017/10/23
DOI:10.1002/ange.201707553
AbstractBenzodisilacyclobutadienes 2 a–c were isolated as blue to green crystalline solids from the reaction of stable disilyne 1 and 1,2-dibromobenzenes in the presence of potassium graphite. In the solid state, substantial bond alternation was observed within the benzene rings of 2 a–c. In hexane, 2 a–c showed remarkable bathochromic shifts of the ππ* (HOMOLUMO) absorption bands at 625–670 nm. NMR spectra and theoretical calculations indicated that the diamagnetic ring currents of the benzene rings of 2 a–c are considerably reduced by contributions from the antiaromatic 1,2-disilacyclobutadienes. In their entirety, the obtained results indicate that 2 a–c represent 8π-electron systems that contain an antiaromatic 1,2-disilacyclobutadiene.
Co-reporter:Tomohiro Iimura;Naohiko Akasaka;Tomoyuki Kosai
Dalton Transactions 2017 vol. 46(Issue 27) pp:8868-8874
Publication Date(Web):2017/07/11
DOI:10.1039/C7DT01113J
A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt complex. The performance of this complex in the catalytic hydrosilylation of (Me3SiO)2MeSi–H with various terminal alkenes that contain functional groups was comparable to that of the corresponding cyclic dialkylsilylene/DVTMS Pt(0) complex.
Co-reporter:Tomoyuki Kosai;Shintaro Ishida
Dalton Transactions 2017 vol. 46(Issue 34) pp:11271-11281
Publication Date(Web):2017/08/29
DOI:10.1039/C7DT02357J
Although many stable disilenes (silicon–silicon doubly-bonded compounds) containing organic π-electron systems have been reported, stable disilenes with heteroaromatic groups remain rare. Herein, we report the synthesis of monodisilenyl-substituted thiophene 1, anthracene 4, acridine 5, and mesitylene 7 and bis(disilenyl)-substituted thiophene 2, 2,2′-bithiophene 3, and anthracene 6via reactions of dialkylmesityldisilenide 8 with the corresponding haloarenes. Disilenes 1–7 show absorption bands with contributions of intramolecular charge transfer (ICT) transitions from π(disilene) to π*(aryl). In the ICT transitions, (bi)thienyl groups as well as anthryl and acrydinyl groups serve as electron acceptors for the SiSi double bonds.
Co-reporter:Tomoyuki Kosai, Shintaro Ishida, and Takeaki Iwamoto
Journal of the American Chemical Society 2016 Volume 139(Issue 1) pp:99-102
Publication Date(Web):December 19, 2016
DOI:10.1021/jacs.6b11912
Although the synthesis of several bis(disilenes) has already been reported, the number of reported conjugation modes between the Si═Si double bonds remains limited. Herein, we report the properties of the stable pentasila-1,4-diene 1, which was obtained from the reaction of two equivalents of disilenide 4 with dichlorodimethylsilane. The π(Si═Si)→π*(Si═Si) absorption band of 1 is considerably broadened and red-shifted compared to those of the corresponding monodisilene and hexasila-1,5-diene, but blue-shifted relative to those of typical tetrasila-1,3-dienes. The bathochromic shift and the broadening of the absorption band in 1 should be attributed to the homoconjugation between Si═Si double bonds through the SiMe2 unit.
Co-reporter:Shintaro Ishida, Takeaki Iwamoto
Coordination Chemistry Reviews 2016 Volume 314() pp:34-63
Publication Date(Web):1 May 2016
DOI:10.1016/j.ccr.2015.11.007
•Synthesis and molecular structures of η2-disilene and η2-disilyne mononuclear complexes are discussed.•Structural parameters and 29Si resonances of η2-disilene and η2-disilyne mononuclear complexes are comprehensively tabulated.•Related transition metal complexes with η2-dimetallenes of heavy group-14 elements are briefly summarized.Recent progress of η2-disilene and η2-disilylne mononuclear transition metal complexes and related complexes are summarized. Although examples for disilene-transition metal complexes are still limited for group 4, 6, 8, 10 and 11 metals, η2-disilene transition metals complexes have been synthesized by various synthetic methods and structural characteristics are well discussed by using X-ray diffraction analysis, 29Si NMR resonances and Dewar–Chatt–Duncanson model. Reactions of these complexes have been also investigated. Very recently, η2-disilyne-group 10 metal complexes have been synthesized. In addition, transition metal complexes with doubly-bonded silicon compounds such as silenes (R2SiCR′2), silanimines (R2SiNR′), silanones (R2SiO) and related doubly-bonded germanium and tin compounds as η2-ligands are briefly summarized.
Co-reporter:Tomohiro Iimura, Naohiko Akasaka, and Takeaki Iwamoto
Organometallics 2016 Volume 35(Issue 24) pp:4071-4076
Publication Date(Web):December 14, 2016
DOI:10.1021/acs.organomet.6b00741
A platinum(0) complex, bearing a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) and an isolable dialkylsilylene ligand, was successfully synthesized by the reaction between the dialkylsilylene and Karstedt’s catalyst. The downfield-shifted 29Si NMR resonance, the smaller 1JSi,Pt value, and the longer Si–Pt distance in this complex relative to the corresponding parameters in related bis(phosphine)-coordinated silylene-platinum complexes suggest weaker π-back-donation from the Pt center to the silylene, which is, however, still significant when compared to related DVTMS-ligated Pt complexes bearing N-heterocyclic carbenes, N-heterocyclic two-coordinate silylenes, or base-stabilized three-coordinate silylenes. The title complex displays excellent catalytic activity in the hydrosilylation of terminal olefins that contain functional groups such as epoxide and amine moieties.
Co-reporter:Fumiya Hirakawa, Hitomi Ichikawa, Shintaro Ishida, and Takeaki Iwamoto
Organometallics 2015 Volume 34(Issue 12) pp:2714-2716
Publication Date(Web):May 26, 2015
DOI:10.1021/acs.organomet.5b00323
A stable dialkylphosphinyl radical, 2,2,5,5-tatrakis(trimethylsilyl)-1-phosphacyclopentan-1-yl (RH2P•), showed both irreversible one-electron oxidation and reduction peaks at −0.24 and −2.29 V vs ferrocene/ferrocenium couple. One-electron reduction of RH2P• with KC8 in the presence of 18-crown-6 (18-c-6) or [2.2.2]cryptand (crypt-222) gave the corresponding phosphides [K(18-c-6)]+[RH2P]− and [K(crypt-222)]+[RH2P]−. Whereas [K(18-c-6)]+[RH2P]− exists as a contact ion pair, [K(crypt-222)]+[RH2P]− exists as a solvent-separated ion pair in the solid state. Reaction of RH2P• with AgOTf afforded an unexpected product, a silver(I) phosphaalkene complex.
Co-reporter:Shintaro Ishida;Kenya Uchida
Heteroatom Chemistry 2014 Volume 25( Issue 5) pp:348-353
Publication Date(Web):
DOI:10.1002/hc.21162

ABSTRACT

The reaction of isolable dialkylsilylene 1 with benzil gave [1+4] cycloadduct 1,3-dioxa-2-sila-cyclopent-4-ene 2 and unexpected 2,5-dioxa-3-silabicyclo[2.1.0]pentane derivative 3. Compound 3 slowly isomerized to 2. The global reaction route mapping method of the model compounds suggests that three reaction paths from an initial silylene–ketone complex (carbonyl silaylide) to 2. A large ring strain energy of model compound for 3 (3′) (218.9 kJ·mol−1) was estimated by density functional theory calculations.

Co-reporter:Daiki Motomatsu;Dr. Shintaro Ishida;Dr. Koichi Ohno;Dr. Takeaki Iwamoto
Chemistry - A European Journal 2014 Volume 20( Issue 30) pp:9424-9430
Publication Date(Web):
DOI:10.1002/chem.201402868

Abstract

A new 2,3-disila-1,3-butadiene (3) was synthesized as pale yellow crystals by a double sila-Peterson reaction of 1,1,2,2-tetrasilyl-1,2-dilithiodisilane with two equivalents of 2-adamantanone at 0 °C. In the solid state, the two SiC bonds adopt a synclinal conformation with a dihedral angle of 76.8(1)°. UV/Vis spectra show two distinct absorption bands, assignable to the π(SiC)π*(SiC) transition, at 371 and 322 nm and the former is considerably redshifted compared with that of structurally similar silenes. The 2,3-disilabutadiene isomerizes to the corresponding 1,3-disilabicyclo[1.1.0]butane with the activation parameters of ΔH=74.5±5.4 kJ mol−1 and ΔS=−71.1±17.1 J mol−1 K−1. DFT studies suggest that the isomerization proceeds through a conrotatory route rather than a disrotatory route. H2O and 9,10-phenanthrenequinone added across each SiC bond in the 2,3-disila-1,3-butadiene. The UV/Vis spectrum and reactivity of 3 suggest that the interaction between the two SiC bonds in 3 would be significant but rather small compared with that between SiSi bonds in a synclinal tetrasilabutadiene.

Co-reporter:Takaki Fukuoka;Kenya Uchida;Dr. Young Mo Sung;Dr. Ji-Young Shin;Dr. Shintaro Ishida;Dr. Jong Min Lim;Dr. Satoru Hiroto;Dr. Ko Furukawa;Dr. Dongho Kim;Dr. Takeaki Iwamoto;Dr. Hiroshi Shinokubo
Angewandte Chemie International Edition 2014 Volume 53( Issue 6) pp:1506-1509
Publication Date(Web):
DOI:10.1002/anie.201309921

Abstract

The treatment of an antiaromatic norcorrole NiII complex with a kinetically stabilized silylene provided ring-expansion products in excellent yields through the highly regio- and stereoselective insertion into the β-β pyrrolic CC bonds. The resultant NiII porphyrinoid monoinsertion product exhibited relatively strong near-IR absorption bands due to the small HOMO–LUMO gap in spite of the disrupted cyclic π-conjugation by the silicon atom.

Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:11172-11176
Publication Date(Web):
DOI:10.1002/anie.201405509

Abstract

Stibinyl and bismuthinyl radicals are recognized as representative intermediates of antimony and bismuth compounds, but still elusive in the condensed phase. We successfully synthesized persistent stibinyl and bismuthinyl radicals in solution by facile dissociation of the corresponding dimers with bulky substituents. We characterized the radicals by NMR and UV/Vis spectroscopy and estimated the thermodynamic parameters for the dissociation equilibria. The radicals show np (HOMOSOMO) transition bands at 497 nm (stibinyl) and 543 nm (bismuthinyl) in 3-methylpentane and react with a stable nitroxyl radical to give the cross-radical coupling products in good yields.

Co-reporter:Dr. Shintaro Ishida;Fumiya Hirakawa;Dr. Ko Furukawa;Dr. Kenji Yoza;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:
Publication Date(Web):
DOI:10.1002/anie.201484271
Co-reporter:Takeaki Iwamoto ; Nobuyoshi Ohnishi ; Naohiko Akasaka ; Koichi Ohno ;Shintaro Ishida
Journal of the American Chemical Society 2013 Volume 135(Issue 29) pp:10606-10609
Publication Date(Web):July 8, 2013
DOI:10.1021/ja404045f
An anthryl-substituted exocyclic silene, 3-silylene-2-silaaziridine, was synthesized by isomerization of the corresponding disilacyclopropanimine. The UV–vis spectrum of the silene shows a distinct intramolecular charge transfer (ICT) transition from the π orbital of the Si═C double bond to the π* orbital of the anthryl moiety. The relatively high-lying π(Si═C) orbital of the 3-silylene-2-silaaziridine moiety and the low-lying π* orbital of the anthryl group would be responsible for the distinct ICT band.
Co-reporter:Dr. Shintaro Ishida;Ryutaro Sugawara;Yoshifumi Misawa ;Dr. Takeaki Iwamoto
Angewandte Chemie International Edition 2013 Volume 52( Issue 49) pp:12869-12873
Publication Date(Web):
DOI:10.1002/anie.201308517
Co-reporter:Takashi Abe ; Ryoji Tanaka ; Shintaro Ishida ; Mitsuo Kira
Journal of the American Chemical Society 2012 Volume 134(Issue 49) pp:20029-20032
Publication Date(Web):November 21, 2012
DOI:10.1021/ja310391m
The new isolable dialkylsilylene 3 bearing a bidentate alkyl substituent was synthesized. Recrystallization of silylene 3 gave yellow crystals of 3 and orange-red crystals of tetraalkyldisilene 4, a dimer of 3. In the solid state, 3 exists as a monomer with a closest distance of 6.745 Å between dicoordinate silicon atoms, while disilene 4 has a remarkably long Si═Si double bond distance of 2.252 Å. An equilibrium between 3 and 4 in solution was observed by NMR and UV–vis spectroscopies, and the thermodynamic parameters of the equilibrium were estimated to be ΔH = −36 ± 3 kJ mol–1 and ΔS = −170 ± 15 J mol–1 K–1. Analysis of the percent buried volume, a measure of the steric demand around the divalent silicon, showed that the flexible steric bulkiness of the alkyl substituent of 3 and 4 allows the reversible dimerization of silylene 3 to disilene 4 and the isolation of both species.
Co-reporter:Shintaro Ishida, Kenya Uchida, Tsunenobu Onodera, Hidetoshi Oikawa, Mitsuo Kira, and Takeaki Iwamoto
Organometallics 2012 Volume 31(Issue 17) pp:5983-5985
Publication Date(Web):August 9, 2012
DOI:10.1021/om3005178
Cycloaddition of an isolable dialkylsilylene converted nonemissive 2,3,4,5-tetraphenylcyclopentadienone to an emissive siloxycyclopentadiene, which shows aggregation-enhanced emission behavior with a light blue fluorescence (λem = 474 nm, ΦF = 0.11) in the solid state rather than in solution.
Co-reporter:Dr. Takeaki Iwamoto;Daisuke Tsushima;Dr. Eunsang Kwon;Dr. Shintaro Ishida;Dr. Hiroyuki Isobe
Angewandte Chemie 2012 Volume 124( Issue 10) pp:2390-2394
Publication Date(Web):
DOI:10.1002/ange.201106422
Co-reporter:Dr. Takeaki Iwamoto;Daisuke Tsushima;Dr. Eunsang Kwon;Dr. Shintaro Ishida;Dr. Hiroyuki Isobe
Angewandte Chemie International Edition 2012 Volume 51( Issue 10) pp:2340-2344
Publication Date(Web):
DOI:10.1002/anie.201106422
Co-reporter:Dr. Takeaki Iwamoto;Fumiya Hirakawa ;Dr. Shintaro Ishida
Angewandte Chemie International Edition 2012 Volume 51( Issue 48) pp:12111-12114
Publication Date(Web):
DOI:10.1002/anie.201206997
Co-reporter:Dr. Takeaki Iwamoto;Fumiya Hirakawa ;Dr. Shintaro Ishida
Angewandte Chemie 2012 Volume 124( Issue 48) pp:12277-12280
Publication Date(Web):
DOI:10.1002/ange.201206997
Co-reporter:Shintaro Ishida, Fumiya Hirakawa, and Takeaki Iwamoto
Journal of the American Chemical Society 2011 Volume 133(Issue 33) pp:12968-12971
Publication Date(Web):July 20, 2011
DOI:10.1021/ja205001m
Dialkylphosphinyl radical 1 was synthesized as thermally stable yellow crystals and found to be monomeric both in solution and in the solid state. EPR spectrum showed that the spin density of 1 is mainly localized on the 3p orbital of the dicoordinated phosphorus atom. A distinct absorption band due to the electronic transition from nonbonding electron pair orbital to singly occupied 3p orbital on the phosphorus atom of 1 was observed at 445 nm in solution. Phosphinyl radical 1 underwent facile reaction with carbon tetrachloride, hydrogen abstraction, and a unique reaction with a persistent radical, galvinoxyl, giving a cyclic phosphaalkene and a silylether.
Co-reporter:Shintaro Ishida;Mitsuo Kira
Heteroatom Chemistry 2011 Volume 22( Issue 3-4) pp:432-437
Publication Date(Web):
DOI:10.1002/hc.20705

Abstract

The reactions of an isolable dialkylsilylene, 2,2,5,5-tetrakis(trimethylsilyl)silacyclopentan-1,1-diyl (1) with ethylene, (Z)-2-butene, acetylene, bis(trimethylsilyl)acetylene, and 2,3-dimethylbutadiene at room temperature gave the corresponding silacycles as isolable compounds. Because of the large steric hindrance, the reaction of 1 with (E)-2-butene gave a complex mixture, indicating no formation of the corresponding silirane. The reaction of 1 with 2,3-dimethylbutadiene afforded the corresponding [1 + 4] cycloadduct without contamination of the [1 + 2] cycloadduct. Stable C-unsubstituted silirane and silirene produced by the reactions of 1 with ethylene and acetylene were analyzed by X-ray crystallography. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:432–437, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20705

Co-reporter:Chieko Watanabe, Yuichiro Inagawa, Takeaki Iwamoto and Mitsuo Kira  
Dalton Transactions 2010 vol. 39(Issue 39) pp:9414-9420
Publication Date(Web):31 Aug 2010
DOI:10.1039/C0DT00415D
A series of dialkylsilylene-group 10 metal complexes (RH2Si)(Me3P)2M (M = Ni, Pd, Pt, RH2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) and novel (η6-arene)(dialkylsilylene)nickel complexes (η6-arene)(RH2Si)Ni were synthesized and characterized by NMR spectroscopy and X-ray analysis. The perpendicular geometry around the Si–M bond and the short Si–M distances of (RH2Si)(Me3P)2M complexes indicate the significant back donation from the metal to the silylene ligand.
Co-reporter:Takeaki Iwamoto;Junichiro Okita;Naoki Yoshida;Mitsuo Kira
Silicon 2010 Volume 2( Issue 4) pp:209-216
Publication Date(Web):2010 October
DOI:10.1007/s12633-011-9069-8
Tetra(t-butyldimethylsilyl)germasilene (8b) was synthesized using di(t-butyldimethylsilyl)hydridogermyllithium prepared by the germa-metallation of the corresponding dihydridogermane. Tetrasilylgermasilene 8b was obtained as single crystals by recrystallization from hexane at rt. The molecular structure of 8b is similar to those of the corresponding disilene 8a and digermene 8c but with an intermediate unsaturated bond length and twist angle between those of 8a and 8c. The reactions of 8b with methanol and 2,3-dimethylbutadiene gave the corresponding adducts. Equilibrium between 8b and the corresponding (trisilylsilyl)(silyl)germylene is suggested by the reaction of 8b with triethylsilane giving the germylene insertion product into the Si–H bond.
Co-reporter:Chieko Watanabe, Yuichiro Inagawa, Takeaki Iwamoto and Mitsuo Kira
Dalton Transactions 2010 - vol. 39(Issue 39) pp:NaN9420-9420
Publication Date(Web):2010/08/31
DOI:10.1039/C0DT00415D
A series of dialkylsilylene-group 10 metal complexes (RH2Si)(Me3P)2M (M = Ni, Pd, Pt, RH2 = 1,1,4,4-tetrakis(trimethylsilyl)butane-1,4-diyl) and novel (η6-arene)(dialkylsilylene)nickel complexes (η6-arene)(RH2Si)Ni were synthesized and characterized by NMR spectroscopy and X-ray analysis. The perpendicular geometry around the Si–M bond and the short Si–M distances of (RH2Si)(Me3P)2M complexes indicate the significant back donation from the metal to the silylene ligand.
Co-reporter:Tomohiro Iimura, Naohiko Akasaka, Tomoyuki Kosai and Takeaki Iwamoto
Dalton Transactions 2017 - vol. 46(Issue 27) pp:NaN8874-8874
Publication Date(Web):2017/05/15
DOI:10.1039/C7DT01113J
A platinum(0) complex bearing a cyclic (alkyl)(amino)silylene and a 1,3-divinyl-1,1,3,3-tetramethyldisiloxane (DVTMS) was synthesized and isolated in the form of colorless crystals. The single-crystal X-ray diffraction analysis of this complex in combination with theoretical calculations indicated that the Pt→Si π-back-donation in this complex is weaker than that in the corresponding cyclic-dialkylsilylene-ligated Pt complex. The performance of this complex in the catalytic hydrosilylation of (Me3SiO)2MeSi–H with various terminal alkenes that contain functional groups was comparable to that of the corresponding cyclic dialkylsilylene/DVTMS Pt(0) complex.
2(1H)-PYRIDINONE, 4,6-DIMETHYL-, HYDRAZONE
Silacyclopent-1-ylidene, 2,2,5,5-tetrakis(trimethylsilyl)-
SILANE, ETHENYLDIMETHYL(1-METHYLETHYL)-
1,1′-dilithioferrocene
disilene
Hydrogen isocyanide
Silane, trichloro(2,4,6-trimethylphenyl)-
1,3-Cyclobutadiene
Bicyclo[2.2.0]hexane
Platinum, bis(tricyclohexylphosphine)-